Immunogenic complex

ABSTRACT

The invention relates to an immunogenic complex comprising at a least one glycoside and at least one lipid, integrated into an iscom complex or matrix, and at least one antigen which antigen is integrated into the iscom complex or coupled on to or mixed with the iscom complex or iscom matrix complex, characterised in that it also comprises at least one enzyme. It also relates to such a complex further comprising at least one peptide which specifically binds to a receptor expressed on a cell capable of antigen presentation, which cell expresses MHC Class I or Class II and to compositions comprising the complexes.

The present invention relates to new immunogenic complexes of iscom or iscom matrix and antigens together with an enzyme and possibly also peptides, which specifically binds to a receptor expressed on a cell capable of antigen presentation, and to compositions comprising the new complexes.

BACKGROUND OF THE INVENTION

Exploitation of the mucosal immune system offers several advantages from a vaccine point of view. Mucosal vaccines may achieve both systemic and local mucosal immune protection against infectious micro-organisms of which many gain access to the body via mucosal membranes. There is a growing interest for oral vaccines and for the possibility of using such vaccines to protect against infectious diseases affecting not only mucosal surfaces but also against diseases like HIV, polio etc.

Mucosally active vaccines containing recombinant protein antigens would have many immunological and economic advantages for inducing protective immunity against a wide variety of mucosal and systemic pathogens.

Recent results show that antigens incorporated into iscoms are highly immunogenic by mucosal routes, inducing strong T cell mediated immune responses that include secretory IgA antibodies, Th1 dependent delayed type hypersensitivity (DTH) and cytokine production, as well as very strong class I MHC restricted CD8⁺ T cell responses. Serum antibody production is also primed, but this is relatively less efficient (3, 11).

The particulate nature of iscoms allows them to preferentially target and activate accessory cells such as macrophages and dendritic cells (DC)(14-17). Iscoms induce normal responses in IL4KO, but not in IL12KO mice (3, 12 and 18). In addition, iscoms stimulate the production of mediators such as IL1, IL6 and IL12 from macrophages and DC and in vivo depletion of macrophages markedly reduces the adjuvant effects of iscoms (15, 18-22).

There is a group of bacterial toxins that exert strong enzymatic activity on mammalian cells, such as E. coli heat-labile toxin (LT) and choler toxin (CT). They act by ADP-ribosylation of GTP-binding proteins in the cell membrane of the target cells, resulting eventually in the formation of large quantities of intracellular cAMP. The increase in cAMP may then act to immunomodulate many diverse immune reactions such as increasing B lymphocyte differentiation, augmenting co-stimulation of antigen-presenting cells, inhibiting or promoting various T cell functions or modulating apoptotis in lymphoid cells. They are therefore potent adjuvants.

CT is composed of five enzymatically inactive, non-toxic B-subunits (CTB) held together in a pentamere structure surrounding a single A-subunit that contains a linker to the pentamere via the A2 fragment (CTA2) and the toxic enzymatically active A1-fragment (CTA1) of the molecule.

The toxic CTA1 has strong ADP-ribosyl transferase activity. This results in activation of adenylate cyclase and the subsequent intracellular increase in cAMP.

CTB binds to the ganglioside GM1-receptor, present on most mammalian cells including lymphocytes and gut epithelial cells. CTB has been integrated in ISCOMS as a mucosa targeting molecule EP 97905539.9 and also together with antigens that do not easily penetrate mucosas EP 97905541.5, in order to direct orally administrated iscoms to the mucosa.

Although it has been shown that CT is a potent inducer of most T cell dependent responses when given orally (3, 4), it has also been reported that it may be less efficient at stimulating CD4⁺ Th1 cells than Th2 cells (5-7). Furthermore, it is not widely accepted as being able to prime CD8⁺ T cells, while the toxicity of intact CT is likely to prevent its use as a practical vaccine vector in man. Recently attempts have been made to overcome this problem by using an artificial adjuvant vector composed of the enzymatically active A1 fragment of CT (CTA1) linked to two Ig binding domains of staphylococcal protein A. The resulting CTA1-DD fusion protein binds B lymphocytes specifically, has no systemic toxicity and has similar adjuvant properties to CT holotoxin when given by parenteral routes (8)+. However, preliminary indications are that it may have only limited effects when given orally.

Whereas B lymphocytes play a central role in the adjuvant effects of CT and in particular, CTA1-DD (8, 13), the particulate nature of iscoms allows them to preferentially target and activate accessory cells such as macrophages and dendritic cells (DC) (14-17). Thus, the mucosal adjuvant effects of CT are dependent on the presence of IL4 dependent B cell follicles in Peyer's patches (PP), but not on IL12 (3, 13). In contrast, iscoms show an opposite pattern of requirements, inducing normal responses in IL4KO, but not in IL12KO mice (3, 17, and 18). In addition whereas CT may inhibit many functions of macrophages, iscoms stimulate the production of mediators such as IL1, IL6 and IL12 from macrophages and DC and in vivo depletion of macrophages markedly reduces the adjuvant effects of iscoms (15, 18-22).

Thus, iscoms and CTA1 and its derivatives use different anatomical routes and immune mechanisms to induce mucosal immune responses.

SUMMARY OF THE INVENTION

It has now turned out that when combining iscoms and an enzyme, especially CTA1 and its derivatives, their adjuvant effects are enhanced, some of their limitations and disadvantages are overcome and that the over all effect unexpectedly may be synergistic. Surprisingly the enzymatic activity of CTA1 is kept intact in the complex. This novel formulation is non-toxic and is highly immuogenic by a variety of mucosal and systemic routes.

The main object of the invention is to provide an immunogenic complex comprising at least one glycoside, at least one lipid and at least one antigen which antigen is integrated into an iscom complex or coupled on to or mixed with an iscom complex or iscom matrix complex, characterized in that it also comprises at least one enzyme.

Another object of the invention is to provide immunogenic iscom complexes, comprising at least one glycoside, at least one lipid and at least one antigen, into which an enzyme preferably A1 subunits of a bacterial enterotoxin have been integrated.

Another object is to provide immunogenic iscom complexes into which both enzymes and peptides or proteins, which specifically binds to a receptor expressed on a cell capable of antigen presentation, have been integrated.

Another object is to provide iscom complexes on to which antigens and enzymes and/or peptides or proteins, which specifically binds to a receptor expressed on a cell capable of antigen presentation, have been coupled.

Another object is to provide iscom complexes mixed with antigens and enzymes and/or peptides or proteins, which specifically binds to a receptor expressed on a cell capable of antigen presentation.

Another object of the invention is to provide immunogenic iscom matrix complexes, comprising at least one glycoside and at least one lipid on to which antigens, enzymes and/or peptides or proteins, which specifically binds to a receptor expressed on a cell capable of antigen presentation have been coupled.

Another object is to provide iscom matrix complexes mixed with antigens and enzymes and/or peptides or proteins, which specifically binds to a receptor expressed on a cell capable of antigen presentation.

Still another object is to provide a complex where the enzyme and a peptide or protein which specifically binds to a receptor is bound together into a fusion protein which is integrated into an iscom complex or coupled on to or mixed with an iscom complex or iscom matrix complex.

Still another object is to provide a complex where the enzyme, the peptide or protein which specifically binds to a receptor and an antigen is bound together into a fusion protein, which is integrated into an iscom complex or coupled on to or mixed with an iscom complex or iscom matrix complex.

Another object is to provide a composition comprising the new complexes according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a immunogenic complex comprising at least one glycoside, at least one lipid and at least one antigen which antigen is integrated into an iscom complex or coupled on to or mixed with an iscom complex or iscom matrix complex, characterized in that it also comprises an enzyme.

The enzyme is preferably an enzyme that confers enzymatic ADP-ribosylating activity as it has turned out that such an enzyme has unexpected adjuvant activity in combination with iscom and iscom matrix complexes. If the enzyme is toxic it is preferred that the toxic put be deleted from the enzyme. Thus, the enzyme may be an enzyme with ADP-ribosylating activity from which a toxic part has been deleted. Especially the enzyme is a native or mutant bacterial toxin, preferably an enterotoxin and specifically a subunit of a toxin that confers enzymatic ADP-ribosylating activity. The enzyme may be selected from Cholera toxin (CT), E. Coli heat labile enterotoxin (LT), Pertussis, Clostridia, Shigella and Peudomonas toxins. Most preferably the enzyme is at least one A1 subunit of a bacterial enterotoxin wherein said enterotoxin is selected from the group consisting of cholera toxin (CT) and E. Coli heat labile enterotoxin (LT). Such enzymes and subunits and the production thereof are described in U.S. Pat. No. 5,917,026.

According to a preferred form of the invention, the immunogenic complex further comprises at least one peptide or protein, which specifically binds to a receptor expressed on a cell capable of antigen presentation. Preferably the cell expresses MHC Class I or Class II antigen. The antigen-presenting cell may be belong the group consisting of lymphocytes, macrophages, dendritic cells, Langerhans cells and epithelial cells.

Iscom contains at least one glycoside, at least one lipid and at least one type of antigenic substances, especially proteins and peptides and can be produced as described in EP 0 109 942 B1, EP 0 242 380 B1 and EP 0 180 564 B1.

Iscom matrices contain at least one glycoside and at least one lipids. Matrices have an is immunostimulating effect on administration together with antigenic substances, and can be produced as described in EP 0 436 620 B1.

The enzyme and/or the antigen and/or the peptide or protein which specifically binds to a receptor may be integrated into an iscom complex. It is also possible to couple one or mote of these substances an to an iscom complex already containing antigens or on to an iscom matrix complex.

Further is it possible to mix on or more of these substances with iscom or iscom matrices. In such a case the iscom complex may already contain one or more antigens and/or one or more enzymes and/or one or more peptides or proteins, which specifically bind to a receptor.

Thus, the invention relates to a composition comprising iscoms wherein one or more antigens, one or more enzymes or one or more receptor binding peptides or proteins are integrated into, coupled on to or mixed with the iscom complex.

The invention also relates to a composition comprising matrix and one or more antigens, one or more enzymes and one or more receptor binding peptides or proteins coupled on to or mixed with the matrix complex.

The antigen-presenting cells having receptors to which the peptide can bind, are suitably cells capable of antigen presentation especially cells expressing MHC Class I and Class II and may be lymphocytes, such as B-lymphocytes, T-cells, monocytes, macrophages, dendritic cells, Langerhans cells, and epithelial and endothelial cells.

The peptide is a peptide that binds to receptors of the above cells, preferably to an Ig or Fc receptor expressed by said antigen-presenting cell and most preferably to receptors of B-lymphocytes.

Examples of specific targeting peptides are peptides capable of binding to receptors of:

-   (i) granulocyte-macrophage colony-stimulating factor (GM-CSF)     capable of binding to the GM-CSF receptor .alpha./.beta.heterodimer     present on monocytes, neutrophils, eosinophils, fibroblasts and     endothelial cells, -   (ii) CD4 and CD8 expressed on T cells which together with the T cell     receptor (TcR) act as co-receptors for MHC class II and MHC class I     molecules, respectively. MHC class I are expressed on most nucleated     cells, whereas MHC class II molecules are expressed on dendritic     cells, B cells, monocytes, macrophages, myeloid and erythroid     precursor cells and some epithelial cells, -   (iii) CD 28 and CTLA-4, two homodimeric proteins expressed mainly on     T cells which bind to B7 expressed on B cells, -   (iiii) CD40 present mainly on the surface of mature B cells which     interact with gp39 expressed on T cells, -   (iiiii) different isotypes of the Ig heavy chain constant regions     which interact with a number of high or low affinity Fc receptors     present on mast cells, basophils, eosinophils, platelets, dendritic     cells, macrophages, NK cells and B cells.

According to a particularly preferred embodiment of the invention, said peptide is constituted by protein A or a fragment thereof in single or multiple copies, such as one or more D subunits thereof.

According to the invention, the enzyme and the peptide which specifically binds to a receptor may be bound together into a fusion protein, which may be integrated into an iscom complex or coupled on to or mixed with an iscom complex or iscom matrix complex.

The fusion proteins comprise a sub-unit of a native or mutant bacterial toxin that confers enzymatic ADP-ribosylating activity, and, lined thereto, a peptide. The peptide is preferably such that the resulting fusion protein is in possession of water solubility and capability of targeting the fusion protein to a specific cell receptor different from receptors binding to the native toxin; thereby mediating intracellular uptake of at least said subunit.

An antigen may also be incorporated in the fusion protein. Thus , the antigen, the receptor binding peptide or protein and the enzyme may be used as a single molecule or as different combinations in fusion proteins for integration into iscoms or coupling on to iscoms and/or matrices or mixing iscoms and/or matrices. One or more antigens, one or more receptor binding peptides or proteins and one or more enzymes may be used as single molecules or in the fusion protein.

The integration of the substances and the coupling thereof on to iscoms or iscom matrices maybe done as described in EP 0 109 942 B1, EP 0 242 380 B1 and 0 180 564 B1.

Although the invention is by no means limited hereto it will be exemplified in the following mainly with reference to the sub-unit A1 of cholera toxin or a mutant thereof.

Preferably the fusion protein comprises the A1 subunit of cholera toxic and is fused to one or more copies of protein A or a fragment thereof, such as the D region of said protein A.

One fusion protein denoted CTA1-DD consisting of CTA1 linked to DD, a dimer of the D-region of protein A, binds to soluble immunoglobulins as well as the Ig-receptor on B cells. The results demonstrate that is molecule lacks enterotoxic activity, but still effectively ADP-ribosylates target protein. When used as a parenteral adjuvant CTA1-DD enhances anti-KLH antibody responses and increases KLH T cell priming.

These results demonstrate the possibility to circumvent the toxic effects of CT simply by removing the CTB pentamer, thus excluding the potential interaction resulting in toxicity between the epithelial cell GM1-receptor and CT. The strategy of targeting of the immunomodulating activity of CTA1 to defined cell populations can be expanded to include essentially any given cell type, enabling specific modulation of cellular responses controlled by cAMP, provided that a suitable targeting molecule is available. CTA1 alone is highly insoluble in physiological aqueous solutions. Thus, the targeting molecule used as fusion partner in this invention also has the important function to enhance solubility of the CTA1 entity.

The CTA1 moiety in CTA1-DD is targeted to B cells primarily, and away from the GM1-receptor on e.g. the gut epithelial cells. Furthermore, using this construct it has been demonstrated that

-   (i) the enzymatic activity of CTA1 was retained in CTA1-fusion     proteins provided that CTA1 was fused at its carboxy terminus; -   (ii) CTA1 in the fusion protein exerts its ADP-ribosyltransferase     activity in target cells through a pathway for entry that is     different from the surface ganglioside GM1-receptor; and that. -   (iii) CTA1-DD displays a strong immunopotentiating activity.

Similarly, CTA1 may be fused to other targeting molecules such as e.g. CD4 to access MHC II expressing cells or any other ligand that specifically can bind to a receptor present on the cell surface. Using this approach CTA1 will not interact with the GM1-receptor present on most mammalian cells including gut epithelial cells because the CTB portion is lacking in the construct. There fore, CTA1 is given a narrow spectrum of cellular interactions via specific binding to surface Ig or Fc-receptors thereby targeting CTA1 to primary B cells, and macrophages and other Fc-receptor carrying cells.

Fusion proteins may be produced by general biotechnological methods known in the art. Fusion protein CTA1DD may be produced as described in U.S. Pat. No. 5,917,026. Fusion proteins with CTA1DD any be produced using the vector described in FIG. 7 or as described in references 8, 29.

The pharmaceutical compositions may comprise one or more immunogenic complexes according to the invention, together with one or more excipients that are acceptable in pharmaceutical or veterinary products, whereby complexes and components to be mixed therewith may be placed in separate compartments.

The compositions according to the invention will in practice normally be administered orally but may be given topically, or by rectal administration or by injection.

For oral administration tablets and capsules may contain conventional excipients, such as binders, for example syrup, sorbitol, or polyvinyl pyrrolidone; fillers, for example lactose, microcrystalline cellulose, corn starch, calcium phosphate or sorbitol; lubricants, for example magnesium stearate, stearic acid, polyethylene glycol or silica; desintegrants, for example potato starch or sodium starch glycolate, or surfactants, such as sodium lauryl sulphate.

Oral liquid preparations can be in the form of for example water or oil suspensions, solutions, emulsions, syrups or elixirs, or can be supplied as a dry product for constitution with water or another suitable vehicle before use.

A composition according to the invention can be formulated for parenteral administration by injection or continuous infusion. Compositions for injection can be provided in unit dose form and can take a form such as suspension, solution or emulsion in oil or aqueous carriers and can contain formulating agents, such as suspending, stabilizing and/or disperging agents. Alternatively, the active constituent can be present in powder form for constitution with a suitable carrier, for example sterile pyrogen-free water, before use.

The compositions according to the invention can contain between 0.1 and 99% by weight of the active constituent, suitably from 30 to 95% for tablets and capsules and 3 to 50% for liquid preparations.

The experimental part shows that iscoms containing a fusion protein comprising CTA1-DD linked to the OVA 323-339 peptide epitope, used as a model antigen, were highly immunogenic when given by the subcutaneous, oral or nasal routes, inducing a wide range of systemic T cell dependent immune responses. No toxicity was observed by any route indicating that rationally designed combined vectors consisting of CTA1-DD and iscoms S may provide the basis of potent and safe mucosal vaccines.

Thus, iscoms containing OVA peptide fused to CTA1-DD were immunogenic when given by a variety of routes, including the oral, nasal and parenteral routes. The responses induced included DTH and serum IgG antibodies in vivo, antigen-specific T cell proliferation and γIFN production in vitro. Despite the fact that it was not possible to detect IL5 production when CTA1-DD-ISCOMS primed lymphocytes were restimulated with OVA in vitro, immunised mice were primed for the production of both IgG2a and IgG1 isotypes, indicating that Th1 and Th2 cells were primed in vivo.

The immune responses induced by iscoms containing the OVA peptide fused to the intact CTA1-DD construct were markedly superior to those found after immunisation with iscoms containing the CTA1-R72K-DD construct which contains a point mutation that abolishes the enzymatic activity of CTA1. This confirms our previous findings that ADP-ribosylating function is essential for the adjuvant property of the CTA1-DD Vector (8) and indicates that a significant proporon of the combined ISCOMS-CTA1DD structure also depends on targeting this activity to the immune system. Nevertheless, iscoms containing the enzymatically inert CTA1-R72K-DD molecule did retain some adjuvant activity when given by mucosal or parenteral routes. This may reflect the well-established adjuvant properties of the iscoms themselves, perhaps enhanced by the ability of the DD fragment to target them in vivo, presumably to B lymphocytes. Thus, in addition to being targeted to DC and/or macrophages like conventional iscoms (14-16, 17), the new, combined vector may have the additional ability to interact with B cells, creating a second potential source of APC for T cell priming. In addition to its potent APC targeting properties, the intact CTA1-DD-ISCOMS adjuvant has the great advantage of being able to activate these cells, creating a costimulatory microenvironment for efficient T cell priming. Iscoms induce DC and/or macrophages to produce proinflammatory cytokines such as IL1, IL6 and IL12 in vivo (15, 18-22), while CTA1-DD is a potent co-activator of B cells (8). For these reasons, at least three important features of CTA1-DD-ISCOMS were considered to contribute to their immunogenicity. First they can physically target antigen and adjuvant to distinct APC populations in vivo and via distinct mechanisms. In the case of iscoms, this probably involves phagocytic uptake by mononuclear cells, whereas CTA1-DD involves receptor-mediated binding and uptake by surface immunoglobulin (8). Secondly, the vector contains two active adjuvants, Quil A and the ADP-ribosylating enzyme CTA1, which can stimulate the relevant cells that have taken up the vector. Lastly, insertion of the antigenic construct into the rigid iscoms particle ensures that the antigen and the adjuvants ate delivered directly to the same APC, focussing their effects for optimal T cell priming.

Extremely low doses of OVA peptide were able to prime systemic immunity by both mucosal and parenteral routes using the CTA1-DD-ISCOMS vector, with as little as 150 ng or 750 ng peptide equivalent being effective by the subcutaneous and oral routes respectively. Secondly, although the antigenic epitope used was delivered as part of a large fusion protein inserted in an iscoms particle, it induced strong immune responses that could be recalled with intact OVA protein. This indicates that CTA1-DD fusion protein and the iscoms vector did not interfere with the antigen processing mechanisms, which normally generate this class II MHC-restricted epitope.

Taken together the results suggest that the combined vector gains access to physiologically relevant antigen processing pathways in an extremely efficient manner. Lastly, it is important to emphasise that no toxicity was observed in mice given the combined adjuvant vectors by any route. This contracts with the toxicity occasionally seen using vectors containing intact Quil A (12, 27, 28), but extends our previous findings that the Quadri A fraction of Quil A and the CTA1-DD fusion protein are themselves lacking significant toxicity, despite their potent adjuvant activities. Thus the combined vector should provide a safe means of inducing mucosal and systemic immunity.

One surprising finding from the study was at the free CTA1-DD fusion protein also had some adjuvant activity when given by the oral route (FIG. 3). As confirmed here, previous studies had shown that this material was active by parenteral and subcutaneous routes (8), but it was considered it unlikely that it would be able to gain access to the B cells necessary for its adjuvant effects when given into the harsh environment of the intestine. However, it is now shown that oral immunization with CTA1-DD containing a defined peptide epitope induces a wide range of immune responses, which interestingly included marked levels of γIFN, despite other claims that CT based adjuvants stimulate predominantly Th2 dependent responses by this route. The responses induced by free CTA1-OVAp-DD were not as high as those, which occurred, when the fusion protein was inserted in iscoms, underling the added potency of the combined vector. However, the enzymatically inactive CTA-R72K-OVAp protein was unable to induce any response above that generated by peptide alone by the oral or parenteral routes, indicating that the adjuvant properties of the intact CTA1-DD material were dependent on its ADP ribosylating activity, even when give by the oral route.

Subcutaneous immunisation gives a synergistic between the CTA1-DD and iscom adjuvant effect in proliferation for CTA1-OVAp-DD-ISCOMS over the sum of the proliferation levels of CTA1-OVAp-DD and CTA1-OVAp-R72K-DD (FIG. 2A). Similarly oral immunisation gives a synergistic effect in IgG2a induction for (FIG. 3D) and in proliferation and γIFN induction for (FIGS. 4A and 4B). Also, intranasal administration gives a synergistic effect in proliferation and γIFN induction as can be seen from FIG. 5.

Together, the results are encouraging evidence that by combining the distinctive adjuvant properties of iscoms and the novel, non-toxic CTA1-DD derivative, it may prove possible to construct effective, safe and stable subunit vaccines which are active by mucosal routes.

All cited references herein are incorporated by reference. The invention will now be further described by non-limiting specific examples with reference to the appended drawings, wherein:

FIGURE LEGENDS

FIG. 1:

Induction of systemic immune responses by subcutaneous immunization with iscoms containing CTA1-OVAp-DD or enzymatically inactive CTA1-R72K-OVAp-DD. Control mice received CTA1-OVAp-DD alone, or OVA 323-339 peptide alone. All mice received the equivalent of 150 ng OVA peptide and results shown are primary DTH responses measured 7 days after immunization (A), serum total IgG (B), IgG1 (C) and IgG2a (D) antibody levels measured 7 days a subcutaneous challenge with soluble OVA given 7 days after primary immunization. The data are means ±1 standard deviation for 5 mice/group and are representative of 3 similar experiments (**, p<0.05 vs all other groups; ¶¶, p<0.05 vs OVAp alone).

FIG. 2:

Induction of systemic immune responses by subcutaneous immunization with iscoms containing CTA1-OVAp-DD or enzymatically inactive CTA1-R72K-OVAp-DD. Control mice received CTA1-OVAp-DD alone, or OVA 323-339 peptide alone. All mice received the equivalent of 150 ng OVA peptide and results shown are proliferation (A) and γIFN (B) levels measured in draining lymph nodes, measured 7 days after immunization. The data are means ±1 standard deviation for 5 mice/group and are representative of 3 similar experiments (**, p<0.05 vs all other groups; ¶¶, p<0.05 vs OVAp alone).

FIG. 3:

Induction of systemic immune responses by oral immunization with iscoms containing CTA1-OVAp-DD or enzymatically inactive CTA1-R72K-OVAp-DD. Control mice received CTA1-OVAp-DD alone, CTA1-R72K-OVAp-DD, or OVA 323-339 peptide alone. All mice received the equivalent of 750 ng OVA peptide on 6 occasions and the results shown are primary DTH responses measured 7 days after the last immunization (A), serum total IgG (B), IgG1 (C) and IgG2a (D) antibody levels measured 7 days after a subcutaneous challenge with soluble OVA given 7 days after the last immunization. The data are means ±1 standard deviation for 4-5 mice/group and are representative of 3 similar experiments (**, p<0.05 vs all other groups; ¶¶, p<0.05 vs OVAp alone).

FIG. 4;

Induction of systemic immune responses by oral immunization with iscoms containing CTA1-OVAp-DD or enzymatically inactive CTA1-R72K-OVAp-DD. Control mice received CTA1-OVAp-DD alone, CTA1-R72K-OVAp-DD, or OVA 323-339 peptide alone. All mice received the equivalent of 750 ng OVA peptide on 6 occasions and the results shown are proliferation (A) and γ IFN (B) levels measured in draining lymph nodes, measured 7 days after immunization. The data are means ±1 standard deviation for 4-5 mice/group and are representative of 3 similar experiments (**, p<0.05 vs all other groups; ¶¶, p<0.05 vs OVAp alone).

FIG. 5:

Priming of systemic T cells by intranasal immunization with iscoms containing CTA1-OVAp-DD or enzymatically inactive CTA1-R7K-OVAp-DD. Control mice received CTA1-OVAp-DD alone or OVA₃₂₃₋₃₃₉ alone. All mice received the equivalent of 150 ng of OVA peptide, and results shown are proliferation (A) and γ IFN (B) levels measured in the spleen 7 days after immunization. The data are means ±1 SD for five mice per group and are representative of tee similar experiments (**, p<0.05 vs all other groups; ¶¶, p<0.05 vs OVAp alone).

FIG. 6:

Construction of iscoms consisting of (A) CTA1-OVAp-DD and PR8, (B) CTA1R7K-OVAp-DD and PR8 and (C) PR8 antigens alone. The CTA1-OVAp-DD and CTA1R7K-OVAp-DD were detected by a HRP (horse radish peroxidase) conjugated rabbit antibody binding to the DD domain and the PR8 antigens were detected using biotinylated chicken anti-PR8 immunoglobulin (not binding to the DD domain) followed by HRP conjugated streptavidin. The saponins composing the iscom particle were detected by their absorbance at 210 nm.

FIG. 7:

Linear map of CTA1-OVA-DD sequence (SEQ ID NOS 3-6, respectively, in order of appearance) check:1329 from: 1 to: 3798 CTA1-DD expressions vector with 217 enzymes:*. Max Cuts:1.

FIG. 8:

DNA and amino acid sequence (SEQ ID NOS 1 and 2) of CTA1-DD fusion protein.

EXAMPLE 1 Preparation pf CTA1DD Fusion Protein

Preparation of a Cholera Toxin A1 Subunit (CTA1) Fusion Protein was made as described in U.S. Pat. No. 5,917,026.

Escherichia coli strains HB101 and E. coli RV308 were used as bacterial hosts for all cloning and expression work. Standard plasmids and vectors used were: pUC 19 and the PCR.TM. vector (Invitrogen, USA). Restriction enzymes and T4 DNA ligase (Boehringer Mannheim, Germany and New England Biolabs, USA) were used according to the recommendation of the supplier.

The oligonucleotides used in the polymerase chain reaction (PCR) were synthesised with an automated machine (Pharmacia-LKB Gene Assembler Plus, Pharmacia Uppsala, Sweden) and phosphorylated separately using polynucleotide kinase (New England Biolabs, USA). Low melting temperature agarose (NUSIEVE.RTM. GTG, FMC Bioproducts, USA) was used to isolate DNA fragments, and Multi Purpose agarose (Boehringer Mannheim, Germany) for DNA analysis.

The PCR amplifications were performed using the DNA Thermal cycler and Taq DNA polymerase (Perkin-Elmer Cetus Instruments, USA).

The bacterial strains were grown in Luria Bertani medium (LB) or yeast tryptone medium (2.times.YT) with ampicillin (Ap) 50 .mu.g/ml or kanaycin (Km) 100 .mu.g/ml. Plasmid DNA was prepared according to MAGIC.RTM. Minipreps DNA Purification Systems manual (Promega, USA).

To determine the nucleotide sequence of the obtained fragments, DNA sequencing was performed using the Sanger method (Sanger, F., Nicklen, S. and Coulson, A. R. DNA sequencing with chain terminating inhibitors. Proc Natl Acad Sci USA. 74, 5463-7, 1977,22). Both strands were sequenced according to a standard protocol for the Taq DYEDEOXY.RTM. Terminator cycle sequencing kit (Applied Biosystems, USA). Analyses were performed on an Applied Biosystems Model 373A DNA Sequencing system.

The gene encoding cholera toxin A1 subunit amino acids 1 to 186 (Mekalanos, J. J., Swartz, D. J., Pearson, G. D., Harford, N., Groyne, F. and de, W. M. Cholera toxin genes: nucleotide sequence, deletion analysis and vaccine development. Nature. 306, 551-7, 1983) was obtained by PCR using two synthetic DNA primer (1 and 2 in FIG. 1 of U.S. Pat. No. 5,917,026). Similarly the DNA segment encoding the IgG-binding region D of staphylococcus aureus protein A (Uhlen, M., Guss, B., Nilsson B., Gatenbeck, S., Philipson, L. and Lindberg, M. Complete Sequence of the Staphylococcal Gene Encoding Protein A. J. Biol. Chem. 1984) was obtained by PCR using two synthetic DNA primers (3 and 4 in FIG. 1 of U.S. Pat. No. 5,917,026).

Using standard molecular biology techniques as described in Sambrook, J. and al., e. Molecular Cloning—A Laboratory Manual.; Second edition ed.; Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.: 19891, plasmid pKP 1001 (FIG. 2 of U.S. Pat. No. 5,917,026) was constructed. Plasmid pKP 1001 contains the gene encoding CTA1 (aa 1-186) fused in frame with a DNA element encoding two tandem copies of the D region from S. aureus protein A. In pKP 1001 the transcription unit encoding the CTA1-DD fusion protein is under control of the tryptophane promoter pTrp.

For the production of the CTA1-DD fusion protein, E. coli RV308 and HB101 cells transformed with plasmid pKP1001 were grown in shaker flasks overnight in 2 times. YT or LB (250 ml or 500 ml), with kanamycin, at 37.degree. C. After culture, the cells were collected by centrifugation. In order to solubilize the intracellularly produced fusion proteins, which precipitated as inclusion bodies, the cell pellet was treated with 6M Guanidine-HCl. After addition of destined water to 1M Guanidine-HCl to allow the protein to refold, the fusion protein was purified by IgG affinity chromatography using IgG Sepharose (Pharmacia, Sweden). After passage of the solubilized fusion protein through the affinity column the gel was washed with TST (50 mM Tris-HCl, pH 7.4, 150 mM NaCl, 0.05% Tween 20), followed buffered with 10 mM ammonium acetate, pH 4.8. Finally the fusion protein was eluated in 0.2 M acetic acid pH 3.1. The eluted fusion protein was stored in aliquots at −20.degree. C. prior to further use. Two other fusion proteins, one comprising CTA1 fused to DD at its amino terminus (DD-CTA1) and a second (CTA1(Asp109->Ala)-DD) consisting of a mutant form of CTA1 in which Asp 109 was converted to Ala by PCR-directed in vitro mutagenesis, were prepared in the same way.

EXAMPLE 2 Preparation of Iscoms

Antigens and Adjuvants

Ovalbumin (Fraction V) was obtained from Sigma (Poole, UK), while OVA 323-339 peptide was obtained from Sigma Genosys, CTA1-DD and CTA1-R72K-DD fusion proteins containing the OVA 323-339 epitope were prepared as described in references 8 and 29, CTA1-R72K is a variant of CTA1 from which one amino acid has been deleted and which lacks enzymatic activity.

For the generation of the fusion proteins CTA1-OVAp-DD and CTA1-R7K-OVAp-DD, harbouring one copy of OVA 323-339 between the DD and the CTA1 moieties, a synthetic oligonucleotide encoding OVA 323-339 flanked by nonpalindromic AvaI sites (31) was inserted bead-to-tail into the BbsI site in vectors pCTA1-DD and pCTA1-R7K-DD. For the production of fusion proteins, Escherichia coli TG-1 cells transformed with the different expression vectors were grown in 250 ml flasks overnight in 2×YT or Luria-Bertani, with 50 μg/ml kanamycin, at 37° C. After culture, the cells were collected by centrifugation, and the fusion proteins, produced as inclusion bodies, were solubilized by treatment with 6 M guanidine-HCl. After addition of distilled water to allow refolding, the fusion proteins were purified by affinity chromatography on IgG-Sepharose (Pharmacia, Peapack, N.J.) and stored in 0.2 M HAc at 4° C.

Iscom-CTA1-R7K-OVA-DD and Iscom-CTA1-OVA-DD

The preparation of these iscoms was done simultaneously. From the stock solution of protein (1 mg/ml) in 0.2 M acetic acid pH 4, both recombinant proteins (CTA1-OVA-DD and CTA1-R7K-OVA-DD) were each dialysed in refrigerator (4-10° C.) against 0.2 M cold phosphate buffer pH 6.

A one ml sample of each dialysed recombinant solution (equivalent to one mg of each protein) were transferred to room temperature.

One mg purified freeze-dried saponin fraction (Quadri A), normally kept in sealed glass containers in freezer below −18° C., were also transferred to room temperature, opened and the glass container with freeze-dried saponin and a small magnetic bar were arranged with clamps over a magnetic stirrer.

A stock solution of 1% lipid mix (1% cholesterol and 1% phoshatidylcholine dissolved in 20% Mega 10), normally kept in sealed plastic vials in freezer (below −18° C.), were also transferred to room temperature and melted at hand temperature (30-40° C.).

The one mL protein sample were added to the freeze-dried saponin and as soon (a few seconds) the saponin were dissolved in the sired protein solution ten 40 microliter of hand warm 1% lipid mix were added and the mixture stirred for the next 3 hours at room temperature. The mixture were then dialysed for the next 2-3 hours at room temperature against 0,2 M room temperate phosphate buffer pH 6. The dialyse was continued in refrigerator (4-10° C.) for one night. Next day the dialysed protein was centrifuged for 5 minutes at 10000×g and the supernatant (0,9 ml) transferred as a 300 microliter overlay to each of three 4 ml ultra centrifugation plastic vials with preformed sucrose freeze gradient. The freeze gradient was on basis of 25% (W/W) sucrose dissolved in 0,2 M phosphate buffer pH 6.

After 5 hours ultra centrifugation (20° C., sw60 rotor, 50000 rpm, r_(sv)=2570000×g) fractions were collected by puncturing the plastic vial with a needle in the bottom. The fractions were analysed for antigenicity, protein content and density. The protein rich fractions, with no free protein were pooled and dialysed in refrigerator (4-10° C.) for 2 days against 0.2 M phosphate buffer pH 6. Finally the iscom preparation was concentrated using centrifugal filter device until desired protein concentration of 0.5 mg/mL was obtained.

Iscom-CTA1DD

This preparation was done as described above using CTA1DD as protein source instead of CTA1-OVA-DD or CTA1-R7K-OVA-DD.

Iscom-Matrix

Saponin Fractionation

Quadri A was prepared as described in Kamstrup S., San Martin R., Doberti A., Grande H., Dalsgaard K,: Preparation and characterisation of quillaja saponin with less heterogeneity than Quil-A. Vaccine Vol. 18, No. 21, 1 Apr. 2000.

From aliquots of 10 mg Quadri A saponin/ml H₂O (kept at −20 C) a sample of 2.5 mg saponin (250 microliter) was added to room temperated 2.183 microliter 0.2 M phosphate buffer pH 6, and placed over magnetic stirrer with small magnet in the same way as described above. Fresh thawn 67 microliter room temperated 1.5% lipidmix (1.5% cholesterol and 1.5% phoshatidylcholine dissolved in 20% Mega 10) were then added.

After 3-5 hours stirring at room temperature the resulting 2.5 ml product was dialysed at room temperature one night and day against 0.2 M phosphate buffer pH 6.

Iscoms containing OVA 323-339 peptide were prepared by EP 97905539.9 and EP 97905541.5. Iscom matrix without protein were prepared by mixing 2.5 mg Quadri A in 250 μl H₂O with 2.183 ml 0.2M PBS pH 6 plus 67 μl lipid mix containing 1.5% cholesterol and 1.5% phoshatidylcholine in 20% Mega10 and sting for 3-5 hours at room temperature. The resulting iscoms were dialysed at room temperature for 36 hours against 0.2 M PBS analysed by EM as above.

EXAMPLE 3 Subcutan Immunisation

Animals

BALB/c mice (H-2d) were purchased from Harlan Olac (Bicester, UK) and maintained under SPF conditions in the Central Research Facility, University of Glasgow, or were obtained from B&K (Sollentuna, Sweden) and bred in the Department of Microbiology and Immunology, University of Gothenburg. All animals were first used at 6-8 weeks of age.

Immunisation of Animals

Mice were immunised subcutaneously into one footpad with iscoms or purified fusion proteins containing 4 μg of CTA1-OVAp-DD, equivalent to 150 ng OVA 323-339 in a total volume of 50 μl. One group of mice received 150 ng OVA 323-339 alone.

Measurement of OVA-Specific Immune Responses In Vivo

7 days after the last immunisation, delayed type hypersensitivity (DTH) were assessed by determining the increment in footpad thickness found 24 hours after subcutaneous injection of 100 μg of heat aggregated OVA in 50 μl of sterile saline. Mice were bled for primary serum antibody responses at this time and also 7 days after DTH challenge to assess secondary responses. Secretory IgA antibody responses were measured 7-10 days after the last feed of antigen in intestinal washes obtained after four gavages with PEG as described previously (9). Total IgG, IgA and IgG1 and IgG2a isotype responses were measured by ELISA, as described previously (10). Local antibody responses were measured in the lung.

Measurement of OVA-Specific Immune Responses In Vitro

7 days after the last immunisation, draining popliteal lymph nodes, spleens or cervical lymph nodes were removed and single cell suspensions prepared in RPMI 1640 (Gibco BRL, Paisley, Scotland) by rubbing through a stainless steel mesh and passing the resulting suspension through Nitex mesh (Cadisch & Sons, London, U.K.). Alter three washes in medium, the cells were resuspended at a final concentration of 10⁶ cells/ml and cultured in 200 μl aliquots in flat bottomed 96 well tissue culture plates (Costar, Nucleopore, High Wycombe, U.K.) in RPMI 1640 containing 10% FCS, 100 U/ml penicillin, 100 mg/ml streptomycin, 50 mg/ml fungizone, 2 mM L-glutamine, 25 mM Hepes, 50 mM 2-mercaptoethanol (all Gibco BRL), either alone or with 1 mg/ml OVA. Proliferation was assessed by addition of 1 μCi/well ³H thymidine for the last 18 hours of culture. Cell bound DNA was harvested on filter mats and ³H-TdR incorporation measured on a Betaplate counter. To measure cytokine production, 4×10⁶ lymph node cells in 1 ml aliquots were cultured in 24 well tissue culture plates (Costar) either in medium alone or with 1 mg/ml OVA. Supernatants were harvested after 2-4 days and stored at −20° C. until assayed. Cytokine production was quantified using sandwich ELISA techniques described in detail elsewhere (3, 21), using appropriate pairs of capture and biotinylated detecting antibodies (all Pharmingen). Antibody binding was detected using extravidin-peroxidase (Sigma) and TMB substrate as described above. Cytokine concentrations in test supernatants were determined with reference to a standard curve constructed using serial dilutions of recombinant cytokines (Pharmingen).

Statistical Analysis

Results are expressed as means +/− 1 SD and comparisons were made using unpaired two tailed Student's t-test.

Results

Incorporation into Iscoms Enhances the Systemic Immunogenicity of CTA1-DD Adjuvant Vector

A. In Vivo Responses

Having successfully incorporated the CTA1-OVAp-DD fusion proteins into iscoms, the immunogenicity of the combined vector was compared with the intact fusion protein. Mice were immunised subcutaneously on one occasion and the subsequent systemic immune responses assessed by measuring primary OVA-specific DTH responses, primary and secondary serum antibody responses and in vitro T cell responses in the draining lymph node.

As anticipated, mice immunised with 150 ng OVA 323-339 in saline showed little or no DTH response above background, whereas mice immunised with purified CTA1-OVAp-DD fusion protein containing the same amount of OVA 323-339 had good DTH responses (FIG. 1A). However, animals receiving CTA1-OVAp-DD fusion protein incorporated it ISCOMS had significantly enhanced DTH responses compared with CTA1-OVAp-DD immunised mice (FIG. 1A). Confirming our previous findings that the enzymatically inactive CTA1-R72K fusion protein lacks inherent adjuvant activity (8), mice receiving CTA1-R72K-OVAp alone had no significant DTH responses above background. However, iscoms containing this material were immunogenic, inducing significant primary DTH responses that were markedly less than those found in mice immunised with CTA1-OVAp-DD-ISCOMS (FIG. 1A), presumably reflecting the known adjuvant properties of the iscom vector itself.

Primary serum antibodies reactive with native OVA could not be detected after immunisation with OVAp in any form (data not shown). However, secondary total IgG antibody responses did occur after subcutaneous challenge with heat aggregated OVA in animals primed with immunogenic vectors. These followed a similar pattern to the DTH responses, with the highest levels of IgG anti-OVA being found in mice immunised with CTA1-OVAp-DD-ISCOMS (FIG. 1B). Significant but lower, IgG responses also occurred in mice given intact CTA1-OVAp-DD fusion protein and in animals receiving CTA1-OVAp-R72K-DD-ISCOMS, whereas mice immunised with OVAp alone or enzymatically inactive CTA1-OVAp-R72K-DD had little or no total IgG antibody in serum (FIG. 1B).

Interestingly, immunisation with CTA1-OVAp-DD-ISCOMS or with CTA1-OVAp-DD primed for both IG1 and IgG2a antibody responses (FIGS. 1C/D), suggesting no bias towards priming of Th1 or Th2 cells by the vectors. Again, some IgG1 and IgG2a responses were found in mice given CTA1-OVAp-R72K-DD-ISCOMS, but not in mice immunised with CTA1-OVAp-R72K-DD itself or with OVAp alone.

B. T Cell Responses In Vitro

Next the immunogenicity of the combined adjuvant vectors was explored in more detail by examining their ability to primed T cell proliferation and cytokine production. Draining popliteal lymph nodes were removed 7 days after primary immunisation and lymphocytes restimulated in vitro with native OVA.

As before, mice immunised with CTA1-OVAp-DD-ISCOMS were primed for very strong T cell proliferation (FIG. 2A) and production of γ IFN (FIG. 2B). Little or no IL5 production was observed. Immunisation with CTA1-OVAp-DD alone, or with iscoms containing the enzymatically inactive CTA1-R72K fusion protein also induced good T cell responses in vitro, although these were significantly lower than those found in CTA1-OVAp-DD-ISCOMS primed animals. Little or no proliferation or cytokine production was observed in mice receiving OVAp alone (FIG. 2). There is a synergistic effect in proliferation for CTA1-OVAp-DD-ISCOMS over the sum of the proliferation levels of CTA1-OVAp-DD and CTA1-OVAp-R72 K-DD (FIG. 2A)

Together, these results confirm that enzymatically active CTA1-DD is an effective adjuvant for a broad range of systemic immune responses when given by parenteral routes and extend earlier findings by showing that incorporation into iscoms markedly enhances this activity.

EXAMPLE 4 Oral Immunisation

Animals were the same as used in example 3. For oral immunisation, mice were fed on days 1, 2, 3, 8, 9 & 10 with iscoms or purified fusion proteins containing 4 μg of CTA1-OVAp-DD, equivalent to 150 ng OVA 323-339. One group of mice received 750 ng OVA 323-339 on each occasion. In vivo and in vivo measurements were performed as in example 3

Results

Incorporation into Iscoms Enhances the Mucosal Immunogenicity of CTA1-DD Adjuvant Vector

Earlier work show that CTA1-DD functions poorly as an adjuvant by the oral route. However, iscoms are extremely effective when given orally and therefore it was examined if incorporation into iscoms could improve the mucosal adjuvant properties of CTA1-DD.

A. In Vivo Responses

Mice were fed on six occasions with the different vectors, a protocol found to be optimal in previous work with iscoms, and systemic immune responses assessed as described above. Oral immunisation with CTA1-OVAp-DD-ISCOMS induced significant DTH responses compared with background levels and these were equivalent to those obtained after subcutaneous priming (FIG. 3A). In these experiments, CTA1-DD itself also primed systemic DTH by the oral route, although to a significantly lesser degree than when incorporated into iscoms. As with the parenteral route, enzymatically inactive CTA1-R72K fusion protein lacks inherent adjuvant activity and mice receiving CTA1R72K-OVAp orally induced no significant DTH responses, but this material was immunogenic when incorporated into iscoms, confirming the inherent mucosal adjuvant properties of iscoms. Again this response was markedly less than that found with iscoms containing intact CTA1-DD protein (FIG. 3A). Mice fed 150 ng OVA 323-339 in saline showed little or no DTH response above background, whereas mice immunised with purified CTA1-OVAp-DD fusion protein containing the same amount of OVA 323-339 had good DTH responses. However, animals receiving CTA1-OVAp-DD fusion protein incorporated in iscoms had significantly enhanced DTH responses compared with CTA1-OVAp-DD immunised mice (FIG. 3A).

Primary serum antibodies reactive with native OVA could not be detected after immunisation with OVAp in any form (data not shown). However, secondary total IgG antibody responses did occur after subcutaneous challenge with heat aggregated OVA in animals primed with immunogenic vectors. These followed a similar pattern to the DTH responses, with the highest levels of IgG anti-OVA being found in mice immunised with CTA1-OVAp-DD-ISCOMS (FIG. 3B). Significant, but lower, IgG responses also occurred in mice given intact CTA1-OVAp-DD fusion protein and in animals receiving CTA1-OVAp-R72K-DD-ISCOMS, whereas mice immunised with OVAp alone or enzymatically inactive CTA1-OVAp-R72K-DD had little or no total IgG antibody in serum (FIG. 3B).

Interestingly, immunisation with CTA1-OVAp-DD-ISCOMS or with CTA1-OVAp-DD primed for both IgG1 and IgG2a antibody responses (FIGS. 3C & D), suggesting no bias towards priming of Th1 or Th2 cells by the vectors. Again, some IgG1 and IgG2a responses were found in mice given CTA1-OVAp-R72K-DD-ISCOMS, but not in mice immunised with CTA1-OVAp-R72K-DD itself or with OVAp alone. There is a synergistic effect in IgG2a induction for CTA1-OVAp-DD-ISCOMS over the sum of the IgG2a levels of CTA1-OVAp-DD and CTA1-OVAp-R72K-DD (FIG. 3D)

B. T Cell Responses In Vitro

As before, mice immunised with CTA1-OVAp-DD-ISCOMS were primed for very strong T cell proliferation and production of γIFN (FIGS. 4A & 4B). Immunisation with CTA1-OVAp-DD alone, or with iscoms containing the enzymatically inactive CTA1-R72K fusion protein also induced good T cell responses in vitro, although these were significantly lower than those found in CTA1-OVAp-DD-ISCOMS primed animals. Little or no proliferation or cytokine production was observed in mice receiving OVAp alone. There are synergistic effects in proliferation and γIFN induction for CTA1-OVAp-DD-ISCOMS over the sum of the proliferation and γIFN levels respectively of CTA1-OVAp-DD and CTA1-OVAp-R72K-DD (FIGS. 4A and 4B)

The results show that a targeted CT derivative can be incorporated into iscoms. The resulting combined vector is a potent adjuvant for inducing a wide range of immune responses to small amounts of peptide immunogen after mucosal and parenteral administration.

EXAMPLE 5 Intranasal Immunisation

Mice were immunized intranasally on three occasions 10 days apart, with iscoms or purified fusion proteins containing 4 μg of CTA1-OVAp-DD or CTA1R7K-OVAp-DD (equivalent to 150 ng of OVA₃₂₃₋₃₃₉) in a total volume of 20 μl. Control groups of mice.

All mice received the equivalent of 150 ng of OVA peptide. FIG. 5 shows the proliferation (A) and IFN-γ (B) levels measured in the spleen 7 days after immunization. It can be seen that there is a synergistic effect in that the level of proliferation and production of IFN-γ when CTA1-OVAp-DD iscoms are used is higher than the sum of the corresponding levels when CTA1R7K-OVAp-DD iscoms are used and CTA1-OVAp-DD.

EXAMPLE 6 Mixed Iscoms Containing Two Antigens

Mixed iscoms containing both CTA1-OVAp-DD and additional antigens (haemagglutinin and neuraminidase from human influenza virus) were prepared essentially according to Example 2.

-   (A) 0.5 mg of each CTA1R7K-OVAp-DD and detergent solubilized PR8     antigens were mixed with 5 mg of saponin (Spikoside, Isconova,     Sweden; 100 mg/ml in distilled water) and 1 mg of each cholesterol     and phosphatidyl choline (15 mg/ml in 20% MEGA-10). -   (B) 0.5 mg of each CTA1-OVAp-DD and detergent solubilized PR8     antigens were mixed with 5 mg of saponin (Spikoside, Isconova,     Sweden; 100 mg/ml in distilled water) and 1 mg of each cholesterol     and phosphatidyl choline (15 mg/ml in 20% MEGA-10). -   (C) 1.0 mg of detergent solubilized PR8 antigens were mixed with 5     mg of saponin (Spikoside, Isconova, Sweden; 100 mg/ml in distilled     water) and 1 mg of each cholesterol and phosphatidyl choline (15     mg/ml in 20% MEGA-10).

The Iscoms were prepared as known in the art (ref. 34). Aliquots of both preparations were analysed by sucrose density gradient centrifugation. The gradients were divided into fractions that were analysed for saponin content (A210) and the two antigens using ELISA. As shown in FIG. 6 both antigens were simultaneously incorporated into the same complex.

Mice were immunised subcutaneously and orally as described in Example 2. Antibody and systemic T cell responses were recorded against OVA and PR8. As shown for OVA in example 2, the response (antibody IgG1 and IgG2a, proliferation and IFN-γ production were enhanced significantly by the simultaneous incorporation of CTA1-OVAp-DD molecule compared to iscoms containing PR8 antigens alone or combined with CTA1R7K-OVAp-DD.

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1. An immunogenic complex comprising: at least one glycoside and at least one lipid, integrated into an iscom complex or matrix; at least one antigen integrated into the iscom complex or coupled onto or mixed with the iscom complex or iscom matrix complex; and an adjuvant comprising (i) an isolated subunit of an A1 subunit of a bacterial enterotoxin selected from the group consisting of cholera toxin and E. coli heat labile enterotoxin, and (ii) a fragment of protein A comprising the D region of protein A, said fragment having the ability to bind to Ig or Fc receptors on an antigen-presenting cell.
 2. The immunogenic complex according to claim 1, characterised in that said antigen-presenting cell expresses MHC Class I or Class II antigen wherein said antigen-presenting cell is selected from the group consisting of lymphocytes, macrophages, dendritic cells, Langerhans cells and epithelial cells.
 3. The immunogenic complex according to claim 1, characterised in that the isolated subunit of an A1 subunit of a bacterial enterotoxin is integrated into an iscom complex comprising at least one glycoside, at least one lipid and at least one antigen.
 4. The immunogenic complex according to claim 1, characterised in that said fragment of protein A is integrated into an iscom complex comprising at least one glycoside, at least one lipid and at least one antigen.
 5. The immunogenic complex according to claim 1, characterised in that said bacterial A1 enterotoxin subunit is the A1 subunit of cholera toxin.
 6. The immunogenic complex according to claim 2, characterised in that the antigen-presenting cell is a lymphocyte.
 7. The immunogenic complex according to claim 1, characterised in that the bacterial A1 enterotoxin subunit and said fragment of protein A are bound together into a fusion protein, which is integrated into an iscom complex or coupled onto or mixed with an iscom complex or iscom matrix complex.
 8. The immunogenic complex according to claim 1, characterised in that the bacterial A1 enterotoxin subunit, said fragment of protein A and an antigen are bound together into a fusion protein, which is integrated into an iscom complex or coupled onto or mixed with an iscom complex or iscom matrix complex.
 9. The immunogenic complex according to claim 7, characterised in that the fusion protein comprises the A1 subunit of cholera toxin fused to one or more copies of said fragment of protein A.
 10. An immunogenic composition comprising the immunogenic complex according to claim 1, characterised in that it further comprises one or more excipients that are acceptable in pharmaceutical or veterinary products.
 11. The immunogenic complex according to claim 1, characterised in that said fragment is a dimer of the D-region of protein A.
 12. The immunogenic complex according to claim 11, characterised in that said adjuvant is a fusion protein CTA1-DD.
 13. The immunogenic complex according to claim 12, characterised in that said antigen is an OVA 323-339 peptide epitope and said adjuvant is CTA1-DD linked to the OVA 323-339 peptide epitope. 